xsk: Fix memory leak for failed bind

Fix a possible memory leak when a bind of an AF_XDP socket fails. When
the fill and completion rings are created, they are tied to the
socket. But when the buffer pool is later created at bind time, the
ownership of these two rings are transferred to the buffer pool as
they might be shared between sockets (and the buffer pool cannot be
created until we know what we are binding to). So, before the buffer
pool is created, these two rings are cleaned up with the socket, and
after they have been transferred they are cleaned up together with
the buffer pool.

The problem is that ownership was transferred before it was absolutely
certain that the buffer pool could be created and initialized
correctly and when one of these errors occurred, the fill and
completion rings did neither belong to the socket nor the pool and
where therefore leaked. Solve this by moving the ownership transfer
to the point where the buffer pool has been completely set up and
there is no way it can fail.

Fixes: 7361f9c3d719 ("xsk: Move fill and completion rings to buffer pool")
Reported-by: syzbot+cfa88ddd0655afa88763@syzkaller.appspotmail.com
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Link: https://lore.kernel.org/bpf/20201214085127.3960-1-magnus.karlsson@gmail.com

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index ac4a317038f1bb90f4c515e813a3c371b301eaaa..c6532d77fde76922066d38e3fbd3d5199f8a1135 100644 (file)
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -878,6 +878,10 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
                }
        }
 
+       /* FQ and CQ are now owned by the buffer pool and cleaned up with it. */
+       xs->fq_tmp = NULL;
+       xs->cq_tmp = NULL;
+
        xs->dev = dev;
        xs->zc = xs->umem->zc;
        xs->queue_id = qid;

diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 67a4494d63b681b80b2bb92428925f2edf5972ee..818b750609220e42560adc26cd8b6601309c4d9c 100644 (file)
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -75,8 +75,6 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
 
        pool->fq = xs->fq_tmp;
        pool->cq = xs->cq_tmp;
-       xs->fq_tmp = NULL;
-       xs->cq_tmp = NULL;
 
        for (i = 0; i < pool->free_heads_cnt; i++) {
                xskb = &pool->heads[i];